Figure 3.

Elevated CD4⁺ Tfh and GC B cells by increased expression of SHM and CSR genes lead to early IgG class switch for A‐eIIV. Vaccine responses were assessed by FACS (a) for CD4⁺ Tfh cells (b) and GC B cells (c) at days 7 and 21 post‐vaccination in the iLN. Expression of AID, Bcl6, IRF4, Pax5 and c‐Myc in B cells from iLN (relative expression to GAPDH expression, expressed in $2^{\mathrm{\Delta }{C}_{\mathrm{t}}}$) at day 7 post‐vaccination (d). Quantity (f) and proportion (g) of H3N2‐1968 HA‐specific IgM and IgG at days 7 and 21 post‐vaccination, measured by ELISA AUC endpoint titres (Supplementary figure 2). Data represent the mean, SEM and individual responses, n = 4 or 5 mice per group. *shows statistical significance by one‐way ANOVA (mixed model) for eIIV versus S‐IIV, *P < 0.05, **P < 0.01 and ***P < 0.005, experiments were repeated twice. Representative FACS plots were gated on lymphocytes for FSC/SSC and live/dead (a).